• 한국의학물리학회지:의학물리
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• 제7권1호
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• pp.53-64
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• 1996

목적 : 별모양무늬를 이용하여 원격 방사선치료기의 회전축의 정확성을 평가할 때 방사선의 진행방향을 고려해야 하는 이론적 근거와 방법을 개발하고, 방사선의 진행방향이 기록되지 않는 경우 길이 방향의 비대칭 조사면을 이용하여 흉내내는 방법을 개발하는 것이다. 방법 : 갠트리 회전축의 기계적 정확성을 평가하기 위해 방사선의 진행방향을 고려하였다. 좁은 조사면에 의해 별모양무늬를 만들어 회전축이라고 어림되는 교점에서 l0cm 떨어진 위치의 측방선량분포를 필름농도계로 측정하여 선축의 좌표를 구하고 하나의 선축에 있는 한 쌍의 좌표를 이용하여 선축의 식을 구한다. 선축과 일치하는 방사선 진행방향의 단위벡터 equation omitted를 구하고 가정된 회전축의 좌표에서 각 선축으로 향하는 벡터 equation omitted와 equation omitted의 벡터곱 equation omitted$\times$equation omitted을 구하여 평균을 취하고 평균에 대한 벡터곱의 최소자승법을 적용하여 회전축의 좌표를 구한다. 그 때 벡터곱의 최대치의 절대값이 구하는 회전축의 정확도이다. 방사선의 진행방향을 고려할 수 없는 콜리메이터와 치료대에 대해서는 진행방향에 대응하는 것으로 긴 방향이 비대칭인 조사면을 이용하였다. 결과 : 동일한 별모양 무늬에 대해 방사선의 진행방향을 고려할 때 회전축의 기계적 정확성이 진행방향을 무시할 때와 다르게 평가되었다. 결론 : 별모양 무늬를 이용하여 원격치료기의 기계적 정확성을 평가할 때는 방사선의 진행방향을 고려하거나 흉내내어 정량적으로 평가해야 한다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1763-1766
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• 2003

Millimeter-wave networking is composed of narrow beam link. it is very substantial that beam connecting point to point is fixed in right direction. It is major requirement in the beam network to keep the beam in best direction. In this paper, We propose the method to find a best suited direction of the antenna's beam using the Genetic Algorithm (GA) in point-to-point link. Proposed method presume that each station knows his direction ${\theta}_1$ , ${\theta}_2$ at every step of GA, then it can be expected that GA is possible to search the ideal solution. Intensity of the received signal is evaluated by the multiplication of lengths to the point which the lobe meets with the horizontal line.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
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• pp.274-277
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• 2003

Millimeter-wave networking is composed of narrow beam link. High directivity of the beam provides either advantage or disadvantage in comparison with conventional wide-lobe microwave communications. In such networks, it is very substantial that beam connecting point to point is fixed in right direction. It is major requirement in the beam network to keep the beam in best direction. In this paper, We propose the method to find a best suited direction of the antenna's beam using the Genetic Algorithm in point-to-point link. Proposed method presume that each station knows his direction $\theta$$_1$,$\theta$$_2$ at every step of Genetic Algorithm, then it can be expected that GA is possible to search the ideal solution. Intensity of the received signal is evaluated by the multiplication of lengths to the point which the lobe meets with the horizontal line.

• Structural Engineering and Mechanics
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• 제30권3호
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• pp.369-382
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• 2008

An oscillator of two lumped masses linked through a vertical spring moves forward in the horizontal direction, initially at a certain height, over a horizontal Euler beam and descends on it due to its own weight. Vibration of the beam and the oscillator is excited at the onset of the ensuing impact. The impact produced by the descending oscillator is assumed to be either perfectly elastic or perfectly plastic. If the impact is perfectly elastic, the oscillator bounces off and hits the beam a number of times as it moves forward in the longitudinal direction of the beam, exchanging its dynamics with that of the beam. If the impact is perfectly plastic, the oscillator (initially) sticks to the beam after its first impact and then may separate and reattach to the beam as it moves along the beam. Further events of separation and reattachment may follow. This interesting and seemingly simple dynamic problem actually displays rather complicated dynamic behaviour and has never been studied in the past. It is found through simulated numerical examples that multiple events of separation and impact can take place for both perfectly elastic impact and perfectly plastic impact (though more of these in the case of perfectly elastic impact) and the dynamic response of the oscillator and the beam looks noisy when there is an event of impact because impact excites higher-frequency components. For the perfectly plastic impact, the oscillator can experience multiple events of consecutive separation from the beam and subsequent reattachment to it.

• 한국광학회지
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• 제8권3호
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• pp.204-208
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• 1997

고리형 레이저에서 단일모드로 발진되는 양방향 광속의 출력세기를 맥스웰-블로흐 방정식을 사용한 준고전적 모형으로 분석하였다. Nd:YAG를 레이저 매질로 설정하고, 한쪽 방향의 광속이 반대 방향의 광속에 미치는 영향을 고려하여, 펌핑률과 감쇄율 및 진동수 어긋남에 따른 레이저 발진의 안정성과 출력변조를 조사하였다. 특히, 전산시늉을 통하여 진동수 어긋남에 따른 출력광속의 변화를 조사하고, 안정한 연속발진 조건을 규명하였다.

• 한국전자파학회논문지
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• 제14권4호
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• pp.413-420
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• 2003

본 논문에서는 위성통신용 능동 위상배열 안테나에서 주파수 스캔 효과에 의하여 발생하는 안테나 빔 패턴의 지향 오차를 보상하는 방법을 제안한다. 능동 위상배열 안테나가 두 개의 빔 패턴을 위하여 두 개의 배열이 직렬 연결되고 배열 수가 비대칭인 경우에, 두 빔의 적용 주파수가 다르고 주파수 간격이 크며 빔 폭이 좁고 스캔각이 크면 안테나는 주파수 스캔 효과에 의해 빔 지향 오차가 발생한다 제안되는 수식을 사용하면, 빔 지향오차 각을 예측하여 계산할 수 있으며 이를 보상하는 능동 위상배열 안테나의 위상제어 값을 계산할 수 있다. 본 논문에서는 첫째 층 32$\times$4 배열과 둘째 층 4$\times$2 배열 구조로부터 두 개의 안테나 빔을 가지고, 7.25 GHz~7.75 GHz 주파수 대역에서 두 빔의 주파수 편차가 최대 500 MHz(6.7 %)이며, 주파수 스캔 범위가 0$^{\circ}$~$\pm$35$^{\circ}$이고, 35.6 dBi 이득과 2.2$^{\circ}$의 3 dB 빔 폭을 가지는 능동 위상배열 안테나 시스템을 제작하고, 주파수 스캔효과에 의한 빔 지향 오차를 제안된 방법의 적용 전과 적용 후에 측정 비교하였다. 주파수 스캔 효과에 의한 빔 지향 오차는 보상 전에 최대 2.5$^{\circ}$였으나, 보상 후에는 최대 0.2$^{\circ}$오차로 감소하였다. 제안된 보상으로 안테나 시스템은 7 dB 신호감쇄가 보상되었다. 제안된 보상으로 능동 위상배열 안테나는 통신을 위한 목표 위성을 정확하게 지향할 수 있다.

• 한국자동차공학회논문집
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• 제10권5호
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• pp.228-234
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• 2002

The CO$_2$ laser beam irradiation strengthening of 35kgf/mm$_2$ grade steel sheet is investigated to reduce the weight of bumper beam. The increase of tensile strength is dominated by the number of fully penetrated melting lines. The optimal laser irradiation pattern is obtained by 3-point bending test of hat-type specimens. Laser should be irradiated not only on the center specimen densely in the width direction, but also on the edge densely in the longitudinal direction. Local laser strengthening may be effective for the weight reduction of automobile bumper beam.

• 반도체디스플레이기술학회지
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• 제18권3호
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• pp.72-76
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• 2019

A Q-switched diode-pumped neodymium-doped yttrium vanadate (YVO₄, λ =1064nm) laser was used for the direct patterning of indium tin oxide (ITO) films on glass substrate. During the laser direct patterning, the laser beam was incident on the two different directions of glass substrate and the laser ablated patterns were compared and analyzed. At a low scanning speed of laser beam, the larger laser etched lines were obtained by laser beam incident in reverse side of glass substrate. On the contrary, at a higher scanning speed, the larger etched pattern sizes were found in case of the beam incidence from front side of glass substrate. Furthermore, it was impossible to find no ablated patterns in some laser beam conditions for the laser beam from reverse side at a much higher scanning speed and repetition rate of laser beam. The laser beam is expected to be transferred and scattered through the glass substrate and the laser beam energy is thought to be also dispersed and much more influenced by the overlapping of each laser beam spot.

• Journal of Biosystems Engineering
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• 제25권2호
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• pp.131-140
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• 2000

Spraying operation is one of the most essential in an orchard management and it is also hazardous to human body. for automatic and unmanned spraying , an autonomous travelling vehicle is demanded. In this study, a telemeter was developed using infrared beam which could detect trunks and obstacles measure distance and direction from the vehicle travelling in the orchard. The telemeter system was composed of two infrared LED transmitters and receivers, a beam scanning device for continuous object detection , two rotary encoders for angle detector, and a beam level controller for uneven soil surface. The detected distance and direction signal s were sent to personal computer which made for the system display the angular and distance measurements through I/O board. According to a field test in an apple farm, the system detected up to 10m distance under 12 V of transmitted beam intensity, however, it was recommended that the proper beam transmit intensity be 7 v at the 10 m distance, because of the negative effect to human body at 12 V. The error rate of this system was 0.92 % when the actual distance was compared to measured one. The system was feasible at the small error rate. The developed telemeter system was an important part for autonomous travelling vehicle provided the real time object recognition . A direction control system could be constructed suing the system. It is expected that the system could greatly contribute to the development of autonomous farm vehicle.

• 한국안전학회지
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• 제6권4호
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• pp.58-65
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• 1991

In - process measurement of surface roughness is introduced which employs an optical method by using laser beam. This makes it possible to detect the surface roughness not only along the circurnferential path but also along the feed direction even during machining. The maximum roughness value is always abtainable from the reading along the feed direction.